On 25-05-2007 05:21, Jason Wessel wrote:
> There is a problem with the calling cancel_rearming_delayed_work if the
> timer was not yet active.
>
> I see this problem when netpoll_cleanup() is called without having done
> any work because it had not processed any packets yet. The problem
> appears to be a result of the loop check
> while(!cancel_delayed_work(dwork)). This endlessly loops because
> del_timer_sync() can return 0 or 1 for success which is passed back as a
> result to the final invariant check for the loop. In this particular
> case zero will always be returned because the timer is not active.
>
> It is possible that the problem exists else where, but I thought I would
> ask if this is expected?
>
> #0 del_timer_sync (timer=0xc7ed90f8) at kernel/timer.c:530
> #1 0xc012f08e in cancel_rearming_delayed_workqueue (wq=0xc7fee800,
> dwork=0xc7ed90e8) at include/linux/workqueue.h:201
> #2 0xc012f0af in cancel_rearming_delayed_work (dwork=0x20)
> at kernel/workqueue.c:680
> #3 0xc0312f78 in netpoll_cleanup (np=0xc880bf40) at net/core/netpoll.c:784
>
> Possible fix.
>
> Signed-off-by: Jason Wessel <[email protected]>
>
> Index: linux-2.6.21/kernel/workqueue.c
> ===================================================================
> --- linux-2.6.21.orig/kernel/workqueue.c
> +++ linux-2.6.21/kernel/workqueue.c
> @@ -666,7 +666,7 @@ EXPORT_SYMBOL(flush_scheduled_work);
> void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
> struct delayed_work *dwork)
> {
> - while (!cancel_delayed_work(dwork))
> + while (cancel_delayed_work(dwork) > 0)
> flush_workqueue(wq);
> }
> EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
It's very optimistic change...
I wonder, how this all could work so long (or how it is supposed
to work now without breaking other callers) with (almost) reversed
condition?
According to this comment:
" * cancel_rearming_delayed_workqueue - reliably kill off a delayed
work whose handler rearms the delayed work."
So, it cannot be used in netpoll_cleanup() if there is no rearming
during this cancel at all. This is a tricky behaviour of course,
and is changed in 2.6.22-rc.
Regards,
Jarek P.
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